The Copper Greenhouse

An attempt to test Willis Eschenbach's Steel greenhouse.

This is not meant to replicate exact mathematical values - impossible withot a lot more work and area! - it is simply to test if thermally conductive but thermally opaque plates cause anomalous temperature rise on the heater.

It should be noted that if the ambient were at 200C instead of 20C then there would still be 1.88 watts heating it up from the ambient.  1.88 watts produces a temperature increase of 50C above AMBIENT

a nuclear core generates 235W/sqm will emit 235 W/sqm to space
Surround this with a steel shell 
When the system has reached stability the shell (which is the same surface area (approx) as the core emits the generated 235 watts (if it did not then the system would not be at stability).

However the shell must emit the same quantity of radiation from both sides. the inward flux is the same as the outward at 235 W/sqm. The core must therefore heat up in order that the shell now receives 235+235 W/sqm

I.e. the core is emitting 470W/sq m


This test simplifies the greenhouse to a heater and copper plate the same size as the heater.
All measurements are made using a digital thermometer with a resolution of 0.1degC

The heat box is similar to that used before - just 2 layers of aluminium foil backed thermal insulation added to outside of box.
A removable thin copper sheet, painted grey, is either hung in front of the heater or removed from the box.

The sensor is placed at exactly 15mm from front of insulation round box.

The temperatures of the hot plate and the sensor are unfortunately affect fractionally by room temperature - This is visible in the results below

 Heating began from room temperature 21C. It reaches a stable temperature of 73.6degC with the copper sheet present and 72.2 degC with the plate absent.

The sensor temperature at the point the copper sheet was removed was 21.6degC the final temperature measured by the sensor was 22.2degC

The emissions from the hot box is therefore no less with the copper removed compared to with the copper in place despite the change in hot plate temperature.

The new setup - This allows for 2 copper plates to be hung between the heater and the fron IR double glazed window
One of the plates can be replaced with  a single plastic IR transmissive sheet.

Note All hanging sheets are approximately the same size as the heater.

The heater is dissipating 1.88 Watts

Box Dimensions
137x130x80 mm - external
80x80x40 mm - internal

heated plate and hanging sheet dimensions
35x35x6 mm approx
The results - Room temperature controlled to +-1deg C

Here we see that with 2 copper plates the temperature is 75.7degC
The sensor in front of the IR window measures 23.25degC
With 1 copper plate the temperature is 75.1degC
The sensor in front of the IR window measures 23.6degC
With 1 copper plate the temperature is 74.05degC
The sensor in front of the IR window measures 24.6degC
With 1 IR transparent plastic plate the temperature is 74.5degC
The sensor in front of the IR window measures 23.6degC
The most significant results here are the 1 copper plate vs the 1 IR transmissive plastic plate. 
The disturbance caused by inserting a plate is the same in both cases
but the heater runs 0.6degC hotter
It is interesting that 2 plates allow the heater to reach a higher temperature than just one (as the iron gh predicts)

Unless the iron greenhouse is accepted I do not see how this result could be explained.

Errors -
GHGs are present
The heater is loosing heat to the back wall
There is not a vacuum between heater and plate.
The box still looses too much heat through its sides.
Ambient has too much effect.
lgl says: March 23, 2013 at 4:42 pm
 why didn’t you use bigger plates, all the way to the walls so that hot air couldn’t leak from the warm side to the cold side?

TFP:  this would have changed the radiating area, I felt it best to keep the plate close to the heater and for the area radiating to be constant so the ir window restrictive size would have similar effect.

A C Osborn says: March 23, 2013 at 4:16 pm
Sorry, your results appear to completely disprove the iron ball/shell theory unless you can show by calculation that 50% of the radiation from the Heat Source equals a rise in the temperature of the heat source of only approximately 1.25 degC.
 Do you really think that the 1.25 degC increase in the heat source represents the 50% increase in the iron ball temperature from the Willis theory?

TFP: This sort of real world kitchen table top experiment in no way can  EXACTLY replicate the iron greenhouse thought experiment.
As I said in the write up, perhaps the most important thing is the the 2 single plate runs the internal stucture of the warm box is the same (a restrictive plate changes the convection in the box in a similar way, so what explains the 0,6degC rise in temperature when the copper plate is present?
I was not looking for exact energy flows (for example I knew that the IR windows are not 100% transmissive, I knew the box is loosing heat through its walls, I do not know what the thermal capacity of the heater is, etc. All this is experiment does (and was expected to do) is show a warming where there shousd according to the slayers be none
A C Osborn says: March 23, 2013 at 5:01 pm

The temperature rose because the interior conditions of the box have been changed.
 For instance the GHGs (air) between the heat source and the plate could have been heated more due to Reflected radiation from the plate, which is not a perfect black body and not re-emitted radiation, which in turn would heat up the source slightly.

TFP yes the internal conditions have change but that is why I tried a IR "invisible" plate in place of the copper. The IR loss in this plate did cause a slight warming of the heater but no where near as much as the single copper plate.

but also remember that the plate will be cooler than the heater and slayer theory says energy cannot travel from cooler to hotter!
tallbloke says: March 23, 2013 at 5:23 pm
Right up until the last line I was with you.

TFP mmmmm! I suppose you are right I'll modify that! removed!!

I believe that this shows that willis's iron greenhouse model is likely to be valid.

Some bolometer stuff

Some radiative transfer stuff:
A good description at the end!

The final proof?

Some really silly stuff:


A Cool Object Reduces Energy loss from a Hot Object

A quick post as the method needs changing.

A heated plate in a well insulated box with 2 IR transmissive windows.
A small window for thermal camera measurements
A larger window to allow passage of IR from/to an external Plate

All wires passing through the insulated box have wires looped and buried in thermal insulation to reduce conduction.
The external plate is 9cm from the IR window. There is no enclosure round the external plate so convection will have no effect on  the internal plate.
Each IR window is double glazed with cling film with an air gap of 2cm.

The internal plate is warmed by a resistor network (12 resistors) evenly spaced on the reverse of the plate (away from window) dissipating a total power of 1.88 watts.

The system was setup as indicated with a ambient temperature external plate and allowed to stabilise (unfortunately not log enough).
The external plate was then replaced with a warm identical plate. This was then allowd to cool.
The cold plate warm plate cycle was repeated. (this time temperatures had stabilised)

External Plate view

Thermal Camera View

Overall view showing holder for external plate

Note that 1st measurement did not allow sufficient time for temperature to stabilise

This shows a significant increase in temperature when the warm plate is in position (0.3C)

NOTE This is not increasing the temperature of the heated plate it is just adding energy to the plate. This therefore is has to warm since the total power input to the plate is greater.

During the last sequence the ambient was measured at a constant 19C

Note IR camera temperatures have been corrected by changing standard emissivit of 0.92 to 0.54 to allow for 2 layers of cling film.

The external plate also has had a double layer of cling film placed between it and the camera.
hot plate on right IR window on Left

IR window on left Cold plate on right (only just visible against background)

Box Dimensions 127x120x80 mm
Internal space 80x80x40 mm

heated plate dimension (Forgot to measure before sealing in compartment)
35x35x6 mm approx

Plate centre is monitored by an attached thermocouple (not used in this test)

This is another experiment showing that a cool object can add energy to a hotter object!

This needs to be repeated with a self heating external object to show that internal temperature will stabilise at a higher value.


Does Thermal Radiation Travel From Cool To Hot Bodies

The Background

There is a belief that the cold atmosphere with CO2 (and other Green House Gases - GHGs) cannot keep the earth warmer than if there were no GHGs. A good source of these comments are WUWT
Michael Moon says: February 6, 2013 at 1:11 pm
Silver Ralph,
You just flunked your first hourly in Thermo. The cooler radiator would be warmed by the warmer radiator, and begin radiating more. If you think this would warm the warmer radiator, then you will fail all your hourlies and never get through school.
Wilis, Joe Public has it exactly right. If you want to know what happens to the flux from a cooler source when it hits a warmer source, the answer is exactly nothing. It is not absorbed, but immediately re-emitted, transferring NO heat.
All these analogies are amusing but ignore Second Law.
The sticking point is usually verbalised as "you cannot warm a hot object with a cool object".  And this is true, but you can slow down the cooling of a hot object by placing a cooler object (that is warmer than the background) next to it.

Radiation travels in straight lines – generally! – and when it leaves the cool object it does not know whether it will hit a hotter or cooler object. It is only the albedo that will determine how much  radiation is reflected or absorbed by the objecty it hits and albedo changes little with temperature in the range considered in climatology.

In the extremes:
If it is a mirror finish in wavelengths considered then no radiation will be absorbed (and since emissivity usually parallels albedo then no radiation will be emitted);
If it is a true black body at the wavelength considered then all radiation hitting it from whatever source will be absorbed (and similary emitted - according to its temperature).

Note that a body may reflect at one wavelength but absorb at another. This effect is not considered here.

Radiation passes both ways from the hot body to the cool AND from the cool body to the hot, the additional energy from the cool body will reduce the net energy flow from the hotter and the hot body will therefore cool more slowly. The radiation from the hot body will reduce the net energy flow from the cool but additionally may actually put more radiation into the cool than is being emitted, thus heating the cool body.
From the above it stands to reason that if both bodies have unchanging internal or external sources of energy  then the hot body temperature will reach a final temperature higher than if the cool body were not present.
Oxygen and Nitrogen molecules do not significantly absorb or emit LW radiation.

Note that the vertical scale is logarithmic each division represents a 10x increase in effect
An atmosphere without GHGs will not impede incoming or outgoing radiation significantly. The body of the earth will receive full solar radiation and it surface would heat up to a temperature that will, as a near black body, radiate the same quantity of radiation directly to space at a temperature of  2.7K (i.e. -270°C).

In addition to the solar radiation the body of the earth would receive radiation from the 2.7K temperature of space.

GHGs absorb some  of the long wave infra red radiation from the body of the earth. These will then almost instantly emitted in all directions. After multiple absorptions and re-emissions there will be effectively 50% up and 50% down. The downward radiation ( “back radiation”) will be from an atmosphere much warmer than the 2.7K of space. The total radiation hitting the earth will be solar+back radiation+2.7K from space. With a warm GHG atmosphere the net radiation is still to space but the body of the earth is receiving addition energy from the GHGs and so will be warmer.

Without GHGs there is very little radiation from the rest of the atmosphere - O2 N2 etc absorb and emit little radiative energy (they will of course conduct and convect). But a gas atmosphere without GHGs will not radiate to space. The body of the earth will of course cool since this will STILL radiate - its radiation passing straight through the O2 N2 molecules.
This experiment attempts prove or disprove the supposition that a warm object cools more slowly in the presence of a cool object (warmer than background but cooler than the hot object).

The test setup:

The sidewalls are approximately 150mm high and the whole unit rests on a wooden bench.

The double layer cling film barrier attempts to stabilise the environment around the hot plate when the cool side changes from a warm object to background condition. It is intended to isolate the hot plate from conduction and convection on the cool side whilst passing IR radiation.

The two plates were heated using a hot air gun. The hot plate is heated to well above the maximum range limit for the camera (120°C). The temperature is then allowed to drop to 120°C whilst the environment stabilised

The temperature difference between hot and warm plates was approximately 18°C at the start of measurement. At 120°C the camera records a sequence at 6.5 frames per second with maximum noise reduction (ie the cameras internal algorithm averages out noise on  the measurements). A reasonably high data rate is chosen to allow averaging to be applied to the data if necessary. 

The picture shows the setup with hot and warm plates (18°C temperature difference) facing each other through a “double glazed” convection and conduction barrier (the vertical black line on the left). The temperature shown between plates is the wall temperature not the air temperature (see earlier post showing that air and water vapour are not picked up on the thermal camera http://climateandstuff.blogspot.co.uk/2012/12/water-vapour-and-thermal-imaging.html)

The wall temperature on the hot side is 43.9°C – this is the temperature of the wall approximately 250 seconds after heating was stopped.

This picture shows the no warm plate scenario approximately 230 seconds from heating having stopped. Note that the wall temperature in the hot compartment - 44.7°C is similar to that in the hot/warm setup - 43.9°C.  The open side of the setup is facing a matt black surface at approximately 21°C. The data from the run is extracted using suitably placed measurement areas on the 2 plates:

Only area AR02 is of interest – the hot plate temperature – although any area can be analysed after recording.

The temperature of each pixel in the defined area (6x19 pixels approximately) is averaged.

The two runs provide series of data with the hot plate cooling from approximately 120°C to 50°C with temperatures measured every 154ms.

The rate of cooling should be the same when cooling from the same temperature with or without the warm plate if the statement "You can slow down the cooling of a hot object by placing a cooler object (that is warmer than the background) next to it" is not true.

The two curves have to be aligned such that at one time period the two temperatures are identical. This is manually adjusted in the spreadsheet (available on request). 120.0431°C (with warm plate) and 120.0784°C (no warm plate) are the closest match temperatures These are at a time of approximately 1 minute from start of recoding.

A second plot has been produced that is sychronised at 67°C. This shows that the result is not just anomaly caused by the heating process

A total of 5700 results per run were obtained and analysed

The Results:

synchronised to 120°C

Synchronised to 67°C


From this it seems clear that when a hot and warm plate are interacting radiatively, the hot plate cools significantly slower than if there is no warm plate.

If the initial data up to 600seconds is ignored there is still an increasing deviation in the plot showing the plate is not cooling as quickly.
Obviously the hot plate does not get hotter - it still cools, but at a slower rate!

Does the thermal barrier pass Infra Red?

The photo below shows the with and without temperature of a hand measured with the camera (it should be noted that the camera response does not extend over the whole IR range – only 2µm to 13µm). The temperature difference shows that 2 layers of "cling film" absorb a significant amount of IR but not ALL of it (hand temperature with clingfilm is 30.2°C and without 35°C ) In order to bring the temperatures of the hand back to 35°C the emissivity correction in the camera has to be changed from 0.92 to 0.58.

Notes: Sources of error Cooling of hotplate will be affected by:
  • Conducted and convective heat loss. These have been minimised by the barrier and the 4 sided corregated card enclosure.
  • Room temperature variation Temperature was measured at 21C before and after each run.
  • Air currents. Minimised by the enclosure and the bench location
  • Radiation from hot surfaces (including the cling film window). This should be the same for both runs (note tat these temperatures will be less than the hot plate so could be considered to be part of the experiment.
Inaccuracies - Most are neglegible:
  • The camera self calibrates before the start of each run.
  • Internal temperature of camera changes during run - because this is a continuous recording the usual timed self calibration is stopped. It is possible that drift may occur. This was minimised by allowing 60 minutes warm up and a fixed ambient temperature. Also both runs would suffer from similar drift.
  • The absolute temperature accuracy will not affect results as the same temperature range is measured
Confirmation bias:
I  obviously would like to show proof of the statements made in the introduction, however the results are extracted and plotted by a simple spread sheet which can be made available, There is no manual operation at this stage.
Calculations are simple and carried out on both sets of data identically

All I can say is that these are the results obtained from this simple experiment without modification.

Please criticise and suggest improvements either email or comment (be_very_careful[at)hotmaildotcom)

Additional stuff.

The results seemed too good to be true so I extracted the data from slightly different areas and redid the spreadsheet calculations.

Note different shape of plate sense areas and AR03 sensing back wall temp on hot side

Synchronising to 120deg C at time 0 Absolute temperature  - note backwall temperatures now included

Synchronised to 120C diffenece between hot plate and warm plate and hot only setups

Resynchronising at 76degC at time zero Absolute temperature

Still get widening temperature gap showing coolingof a hot plate is slowed by a warm plate

So again these 2 runs analysed differently show that a cool object (warmer than background) can slow the cooling of a hot plate


Thoughts for a repeat:
Continuous monitoring of ambient temperature.
Enclose hot plate in box of constructed with thermal insulation with 2 sides of cling film (limits heat loss to mainly IR).
Put constant power into the hot plate (fixed voltage across a resistor) Measure temperature with thermocouple - set to approximately 80C when facing ambient.
With hot plate facing plate atambient temperature
Allow temperature to stabilise
Remove ambient plate (possibly now above ambient)
Replace with warm plate at 70C initially
Allow temperature to "stabilise" should rise then fall as the warm plate cools
Remove warm plate leaving side open to ambient. 

Allow temperature to stabilise
Possible problem is the not quite thermally transparent cling film. - as this heats it will begin radiating. 

Improvement suggestions?